The ethnic tensions that have plagued recent Australian Opens simmered just below the surface on Wednesday as rival groups of Serbians,Croatians and Bosnians engaged in verbal warfare. While the potentially tricky match between Croat Marin Cilic and Serb Janko Tipsarevic passed off largely trouble-free,security was called during a match between Bosnian-born American Amer Delic and Frenchman Paul-Henri Mathieu.

It was deemed necessary after a group of Serbian fans turned up and began taunting Delics supporters. Delic,who overcame Mathieu in five sets,said later he wanted his fans to calm down and not turn his third round match with Serbias Novak Djokovic into World War III.

Im going to try and tell my fans that we dont need to be embarrassing ourselves in front of the world and I hope Novak says something to the Serbian fans also, Delic said. You know,leave the politics aside. Its not my fault and its not Novaks fault.

Ethnic violence erupted on the opening day of the 2007 tournament when Serbian and Croatian fans,wearing the national colours of the bitter Balkan rivals,attacked each other with flagpoles,bottles and boots.

The Serbian fans who descended on the Delic-Mathieu clash came straight from seeing Tipsarevic go down to the big-serving Cilic 6-2,6-3,4-6,6-3. That match ended without incident although both players were upset by fans singing political songs rather than following the tennis.

It was like I expected  it was a highly intense match, Tipsarevic said. Both the Serbs and the Croats were a little bit incorrect singing songs that had nothing to do with the tennis, Tipsarevic said.